1. Field of the Invention
The present invention relates to a power supply device suitable for reducing power consumption, a control method for the power supply device, a portable electronic device, a timepiece, and a control method for the timepiece.
2. Description of the Related Art
Small-sized electronic watches in the form of, e.g., wristwatches have been realized, each of the watches incorporating a power generator in addition to both a clocking circuit for counting time and a driving circuit for driving a motor coupled to a hand moving mechanism. Such devices operate with replaceable batteries. Those electronic watches have a function of charging electric power generated by power generators in capacitors, etc., and indicate the time of day with the power discharged from the capacitors when power is not generated.
Those electronic watches can therefore operate with stability for a long time without batteries. In consideration of the inconvenience of replacing batteries and a problem incidental to disposal of exhausted batteries, it is expected that power generators will be incorporated in more and more electronic watches in the future.
A power generator incorporated in a wristwatch, etc. comprises, for example, a solar cell for converting irradiated light to electrical energy, or a power generating system for capturing motion of the user""s arm, etc. and converting kinetic energy to electrical energy. Such a power generator is very superior in utilizing energy present in environment of the user for conversion to electrical energy, but has problems that utilizable energy density is low and energy cannot be obtained in continuous fashion. Accordingly, power generation can not be continuously performed, and the electronic watch operates with the power accumulated in a capacitor while the power generation is suspended.
Because a power generator incorporated in a small-sized electronic watch has a small electromotive voltage, the voltage produced between terminals of a capacitor is not sufficient to operate a clocking circuit. For this reason, the voltage produced between the terminals of the capacitor is stepped up, and the stepped-up voltage is accumulated in second capacitor. Also, in order so that a stable source voltage is supplied regardless of fluctuations in the stepped-up voltage, the voltage across the second capacitor is stabilized using a constant-voltage circuit, and the stabilized voltage is supplied as a source voltage to the clocking circuit.
In the above electronic watch, to prolong a period of time during which the watch can be continuously used, total power consumption of the electronic watch must be reduced.
However, the constant-voltage circuit, itself, consumes power. It is therefore not preferable to operate the constant-voltage circuit at all times from the viewpoint of reducing power consumption. On the other hand, the constant-voltage circuit is essential to operate the clocking circuit in a stable way without malfunction.
Therefore, it is an object of the present invention to overcome the aforementioned problems.
The present invention has been made in view of the above situations in the art, and its object is to reduce power consumption by operating a constant-voltage circuit in a sampling (intermittent) manner.
Another object of the present invention is to control a constant-voltage circuit in accordance with fluctuations in an input voltage, thereby reducing power consumption and stabilizing a source voltage.
To solve the above problems, a power supply device according to the present invention is characterized in comprising a voltage stabilizer circuit or stabilizing means for producing an output voltage resulting from stabilizing an input voltage when supplied with power, a power supply or power supply means for supplying power to the voltage stabilizing circuit or means, a voltage fluctuation detector or detecting means for detecting a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected, and a controller or control means for controlling the power supply operation of the power supply means in accordance with a result detected by the voltage fluctuation detector or detecting means.
With the above features of the present invention, since the power supply operation of the power supply means can be controlled in accordance with fluctuations in the input voltage, the output voltage can be stabilized and power consumption can be reduced.
More concretely, the control means may control the power supply means so as to supply power to the voltage stabilizing means and stop the supply of power at a certain period when the input voltage is stable. When the voltage fluctuation detecting means detects a fluctuation in the input voltage or a condition in which the a fluctuation in the input voltage is expected, the control means may also cause the power supply means to set a ratio (defined as a time during which power is supplied to the voltage stabilizing means versus a time during which power is stopped) to a greater value than when the input voltage is stable. With the above features of the present invention, when the input voltage fluctuates, the time during which power is supplied can be prolonged so that the output voltage can be stabilized. On the other hand, when the input voltage is stable, the time during which the power supply is stopped can be prolonged so that the power consumption can be reduced.
Also, the control means may control the power supply means so as to intermittently supply power to the voltage stabilizing means when the input voltage is stable, and control the power supply means so as to supply power to the voltage stabilizing means at all times when the voltage fluctuation detecting means detects a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected. In this case, when the input voltage fluctuates, the voltage stabilizing means is operated at all times and therefore the output voltage can be further stabilized.
A portable electronic device according to the present invention is characterized in comprising the above power supply device, power generating means for generating power, and an electricity accumulator or accumulating means for accumulating the power from the power generating means and supplying an accumulated voltage, as the input voltage, to the power supply device. The voltage fluctuation detecting means is constituted as a charging detector or detecting means for detecting charging into the electricity accumulating means. In this case, fluctuations in the input voltage due to an internal resistance of the electricity accumulating means can be monitored by detecting charging into the electricity accumulating means.
In this connection, the charging detecting means may detect charging into the electricity accumulating means in accordance with a charging current flowing into the electricity accumulating means, or may detect charging into the electricity accumulating means in accordance with an electromotive voltage generated by the power generating means.
A portable electronic device according to the present invention is characterized in comprising the above power supply device, power generating means for generating power, first electricity accumulating means for accumulating the power from the power generating means, voltage transforming means for transforming a voltage of the first electricity accumulating means at a transformation amplification depending on the magnitude of the voltage of the first electricity accumulating means, and second electricity accumulating means for accumulating a voltage transformed by the voltage transforming means and supplying an accumulated voltage, as the input voltage, to the power supply device. The voltage fluctuation detecting means being constituted as an amplification change detector or detecting means for detecting a change of the transformation amplification in the voltage transforming means. In this case, fluctuations in the input voltage can be detected in accordance with a change of the transformation amplification.
A portable electronic device according to the present invention is characterized in comprising the above power supply device, a power consumer or consuming means for receiving stabilized power from the input voltage and consuming the received power, the voltage fluctuation detecting means being constituted as power consumption detector or detecting means for detecting an increase of power consumption in the power consuming means. More concretely, the power consuming means is a motor, and the power consumption detecting means detects an increase of power consumption in accordance with a driving supply voltage for the motor. In this case, fluctuations in the input voltage can be detected in accordance with an increase of power consumption.
In the portable electronic device according to the present invention, preferably, the control means controls the power supply means so as to repeat supply of power to the voltage stabilizing means and stop of the power supply at a certain cycle when the input voltage is stable, and controls the power supply means so as to set a ratio of time during which power is supplied to the voltage stabilizing means to time during which the power supply is stopped to a greater value than the ratio set in the case of the input voltage being stable, when the voltage fluctuation detecting means detects a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected. Further, the control means may control the power supply means so as to set a ratio of time during which power is supplied to the voltage stabilizing means to time during which the power supply is stopped to a greater value for a certain preset period than the ratio set in the case of the input voltage being stable, when the voltage fluctuation detecting means detects a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected.
Also, preferably, the control means controls the power supply means so as to intermittently supply power to the voltage stabilizing means when the input voltage is stable, and controls the power supply means so as to supply power to the voltage stabilizing means at all times when the voltage fluctuation detecting means detects a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected. Further, the control means may control the power supply means so as to supply power to the voltage stabilizing means at all times for a certain preset period when the voltage fluctuation detecting means detects a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected.
A timepiece according to the present invention is characterized in comprising the above power supply device, and a clock or clocking means supplied with power by receiving an output voltage from the power supply device and counting time. In this case, the clocking means can be operated with stability, and at the same time power consumption can be reduced.
A timepiece according to the present invention may comprise power generating means for generating power, electricity accumulating means for accumulating the power from the power generating means, voltage stabilizing means for producing an output voltage resulted from stabilizing an input voltage, power supply means for supplying power to the voltage stabilizing means while a voltage accumulated in the electricity accumulating means is employed as the input voltage, voltage fluctuation detecting means for detecting a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected, control means for controlling the power supply operation of the power supply means in accordance with a result detected by the voltage fluctuation detecting means, and clocking means supplied with power by receiving an output voltage from the voltage stabilizing means and counting time.
A timepiece according to the present invention may comprise power generating means for generating power, a first electricity accumulating circuit or means for accumulating the power from the power generating means, a voltage transformer or transforming means for transforming a voltage of the first electricity accumulating means at a transformation amplification depending on the magnitude of the voltage of the first electricity accumulating means, a second electricity accumulating circuit or means for accumulating a voltage transformed by the voltage transforming means and supplying an accumulated voltage, voltage stabilizing means for producing an output voltage resulted from stabilizing an input voltage, a power supply or power supply means for supplying power to the voltage stabilizing means while the voltage accumulated in the second electricity accumulating means is employed as the input voltage, amplification change detector or detecting means for detecting a change of the transformation amplification in the voltage transforming means, a controller or control means for controlling the power supply operation of the power supply means in accordance with a result detected by the amplification change detecting means, and a clock or clocking means supplied with power by receiving the output voltage from the voltage stabilizing means and counting time.
A control method for a power supply device including a constant-voltage circuit for producing an output voltage resulted from stabilizing an input voltage when supplied with power, according to the present invention, is characterized in comprising a first step of supplying power to the constant-voltage circuit for a first preset time, and a second step of stopping the supply of power to the constant-voltage circuit for a second present time after the lapse of the first time, the first step and the second step being repeated alternately subsequent to the end of the second step.
With the above features of the present invention, the constant-voltage circuit alternately repeat the power supply state and the power supply stopped state. The output voltage fluctuates depending on the input voltage in the power supply stopped state, but the output voltage resulted from stabilizing the input voltage is produced in the power supply state, thus resulting in a small fluctuation width of the output voltage. It is therefore possible to reduce power consumption while suppressing the fluctuation width of the output voltage.
A control method for a power supply device including a constant-voltage circuit for producing an output voltage resulted from stabilizing an input voltage when supplied with power, according to the present invention, is characterized in comprising the steps of detecting a fluctuation in the input voltage or a condition in which a fluctuation in the input voltage is expected, and controlling supply of power to the constant-voltage circuit in accordance with a detected result. With the above features of the present invention, since the power supply operation can be controlled in accordance with a fluctuation in the input voltage or a condition in which such a fluctuation is expected, the output voltage can be further stabilized and the power consumption can be further reduced.
A control method for a timepiece including a constant-voltage circuit for producing an output voltage resulted from stabilizing an input voltage when supplied with power, and a clocking circuit supplied with power by receiving the output voltage and counting time, according to the present invention, is characterized in comprising the steps of accumulating generated power in a first electricity accumulator, transforming a voltage of the first electricity accumulator at a transformation amplification depending on the magnitude of the voltage of the first electricity accumulator, accumulating a transformed voltage in a second electricity accumulator and supplying an accumulated voltage, as the input voltage, to the constant-voltage circuit, receiving power supplied from the second electricity accumulator and driving a motor to rotate hands for indicating the time of day in accordance with a result counted by the clocking circuit, detecting at least one of charging into the first electricity accumulator, a change of the transformation amplification, and driving of the motor, and controlling supply of power to the constant-voltage circuit and stop of the power supply in accordance with a detected result.
With the above features of the present invention, a factor that fluctuates the input voltage, i.e., at least one of charging into the first electricity accumulator, a change of the transformation amplification, and driving of the motor is detected. Therefore, the supply of power to the constant-voltage circuit and stop of the power supply can be properly controlled. As a result, the clocking circuit can be operated with stability, and at the same time the power consumption can be reduced.
In the above control method, preferably, when it is determined from the detected result that the input voltage is stable, power is intermittently supplied to the constant-voltage circuit, and when it is determined from the detected result that the input voltage is fluctuated or a fluctuation in the input voltage is expected, a ratio of time during which power is supplied to the constant-voltage circuit to time during which the power supply is stopped is set to a greater value than the ratio set in the case of the input voltage being stable, or power is supplied to the constant-voltage circuit at all times.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.